For example, a mass spectrometer, which ionizes a sample by irradiating the sample with a laser beam under vacuum, accelerates the ions to fly, and separates and detects the flying ions according to their mass-to-charge ratio, is known as a vacuum processing apparatus that processes an object wider vacuum (for example, Patent Literature 1).
In this type of apparatus, for example, a door between a processing chamber and the outside of the apparatus is opened to bring an object in the processing chamber, the door is closed to evacuate the processing chamber, and the object is processed. When the process is ended, the vacuum in the processing chamber is broken, and the door is opened to bring the object out of the processing chamber. However, in this manner, if the vacuum in the processing chamber is broken and the evacuation is performed each time the object is exchanged, it takes much time to replace objects in the processing chamber, and the throughput of the apparatus is very low.
For this reason, sometimes a load lock chamber is provided between the processing chamber and the outside of the apparatus (for example, Patent Literature 2). In the apparatus of Patent Literature 2, a door (first door) separating the outside of the apparatus from the load lock chamber is opened, the object s brought in the load lock chamber, and the load lock chamber is evacuated. When the load lock chamber reaches a preset degree of vacuum, another door (second door) separating the load lock chamber from the processing chamber (which is maintained at the preset degree of vacuum) is opened. Specifically, the second door is constructed with a gate valve. When the second door is opened, a transfer robot disposed in the processing chamber extends an extensible arm to enter a hand to the load lock chamber, grips the object in the load lock chamber, shrinks the arm to return the hand to the processing chamber, and transfers the object to the processing chamber. When the arm retreats from the load lock chamber, the second door is closed and the object is processed in the processing chamber. When the process on the object is ended, the second door is opened. The transfer robot grips the processed object existing in the processing chamber with the hand, advances the hand into the load lock chamber to transfer the object to the load lock chamber, and places the object at a predetermined position in the load lock chamber. Then, after the arm of the transfer robot retreats from the load lock chamber, the second door is closed. When the second door is closed to separate the processing chamber and the load lock chamber, the load lock chamber is opened to the atmosphere, and the object is brought out from the apparatus.
Normally, the size of the load lock chamber is made minimum for exchanging the object with the outside of the apparatus. Thus, the internal volume of the load lock chamber is smaller than the internal volume of the processing chamber in which the equipment or the like necessary for process is disposed. When the load lock chamber is provided in the apparatus, it is only necessary, in exchanging the object, to evacuate the load lock chamber alone which has relatively smaller internal volume, and the necessity of evacuating the processing chamber having a relatively lamer internal volume is reduced.